Wu S N, Yu H S, Seyama Y
Department of Medical Education and Research, Kaohsiung-Veterans General Hospital, Taiwan.
J Biochem. 1996 Jan;119(1):42-8. doi: 10.1093/oxfordjournals.jbchem.a021214.
Spontaneous and vasopressin-induced Ca2+ oscillations in cultured vascular smooth muscle (A7r5) cells were further examined and characterized. Intracellular Ca2+ concentrations ([Ca2+]i) were measured by use of a high-performance laser cytometer. When the oscillatory patterns in [Ca2+]i were analyzed with a power spectrum method, about 80% of cells exhibited spontaneous Ca2+ oscillations with the frequency of 0.02-0.5 Hz. Nifedipine abolished these repetitive spikes, whereas pinacidil partially attenuated their amplitude and frequency. When vasopressin (100 nM) was applied to A7r5 cells, there was an initial rise in [Ca2+]i, followed by a delayed sustained increase in [Ca2+]i. The one-pool, nonoscillatory model was employed to fit this biphasic change, and the difference between the observed response and the simulated response was then analyzed with a power spectral method. About 50% of cells were noted to display oscillatory patterns in [Ca2+]i after sustained increase in [Ca2+]i. The present study indicates that spontaneous Ca2+ oscillations in A7r5 cells are modulated by the activity of ATP-sensitive K+ channels and are not related to pertussis toxin-sensitive GTP-binding protein(s). On the basis of the one-pool, nonoscillatory model, it is suggested that the buffering capacity of internal stores appears to be stronger in the cells with spontaneous Ca2+ oscillations than in those in a quiescent state, and the vasopressin-mediated inhibition of accumulation by internal stores was attenuated when the cells exhibited spontaneous Ca2+ oscillations. The implementation of this minimum kinetic model integrated with a power spectrum method would be an alternative to understand the oscillating behavior in [Ca2+]i.
对培养的血管平滑肌（A7r5）细胞中自发的和血管加压素诱导的Ca2+振荡进行了进一步研究和表征。使用高性能激光细胞仪测量细胞内Ca2+浓度（[Ca2+]i）。当用功率谱方法分析[Ca2+]i中的振荡模式时，约80%的细胞表现出自发的Ca2+振荡，频率为0.02 - 0.5Hz。硝苯地平消除了这些重复的尖峰，而吡那地尔部分减弱了它们的幅度和频率。当向A7r5细胞施加血管加压素（100 nM）时，[Ca2+]i最初升高，随后[Ca2+]i出现延迟的持续升高。采用单池非振荡模型来拟合这种双相变化，然后用功率谱方法分析观察到的反应与模拟反应之间的差异。在[Ca2+]i持续升高后，约50%的细胞被观察到在[Ca2+]i中显示出振荡模式。本研究表明，A7r5细胞中的自发Ca2+振荡受ATP敏感性钾通道活性的调节，且与百日咳毒素敏感的GTP结合蛋白无关。基于单池非振荡模型，提示在具有自发Ca2+振荡的细胞中，内质网的缓冲能力似乎比处于静止状态的细胞更强，并且当细胞表现出自发Ca2+振荡时，血管加压素介导的内质网积累抑制作用减弱。将这种最小动力学模型与功率谱方法相结合的应用将是理解[Ca2+]i振荡行为的一种替代方法。
